Linear belt actuator

ABSTRACT

a linear actuator capable of transmitting tractive forces as well as thrust forces and operating then as a rigid single-piece rod. The linear actuator has two identical actuating belts ( 1, 1 ′) with notches on each of their sides ( 10, 10′; 11, 11 ′) and provided on one first side ( 10, 10 ′) with uniformly spaced blocks ( 2, 2 ′) which mesh with drive members ( 3 ) such that the two actuating belts ( 1, 1 ′) are independent upstream of the drive members ( 3 ), whereas downstream of the drive members, they are integrally assembled so as to define a section extending along a straight line wherein the linear actuator operates like a single-piece rigid rod.

The present invention relates to a linear actuator which can transmittractive forces and also thrust forces, in that case behaving as aunitary rigid bar

Thrust chains suitable for performing this function have already beenproposed. Thrust chains of this type have already been described, forexample, in the documents FR-1 297 285 and FR-2 061 884.

These chains are conventionally constituted by a series of linksarticulated to one another by means of pins that are arrangedtransversely.

Each link comprises two substantially parallel flanges which arepierced, respectively, by two holes for receiving the articulation pinsand each of which is equipped with an extension defining a fronttransverse active face and a rear transverse active face which arecaused to bear against the rear and front transverse active faces,respectively, of the flanges of the adjacent links when the portion ofchain of which the links in question form part extends along a straightline.

Thrust chains of this type are driven, in the region of a curved end, bya device comprising a casing, a rotary pinion which has its axisparallel to the articulation pins of the links and is mounted in thecasing and on which the chain is wound, as well as idle rollers forguiding the links of the chain around the rotary pinion.

Thrust chains of this type can transmit tractive and thrust forces in asatisfactory manner in any direction, including upwards, but have afundamentally sophisticated configuration.

Moreover, these thrust chains are suitable purely for actuating “heavy”mechanical parts and, up to now, a similar device which is designed toenable changes in direction to be performed in small automaticmechanisms has never been proposed.

The object of the present invention is to fill this gap by proposing alinear actuator of the above-mentioned type which is characterized inthat it comprises two identical actuating bolts which are toothed oneach of their faces and are provided, on a first of their faces, withuniformly-spaced studs which mesh by means of drive members in a mannersuch that the two actuating belts are independent upstream of the drivemembers whereas, downstream of those members, they are assembledintegrally so as to define a portion which extends along a straight lineand in which the linear actuator behaves as a unitary rigid bar.

These actuating belts are preferably made of a flexible, reinforcedplastics material and thus correspond to simple and inexpensive elementsalso having the advantage that they can be manufactured by moulding in asingle piece.

According to a preferred characteristic of the invention, the drivemembers are constituted by a casing enclosing two rotary pinions, thatis, a drive pinion and a driven pinion, which engage one another anddrive two endless caterpillar-type bands mounted on one side and on theother side of the actuating belts, respectively, and equipped on theirouter faces with teeth which cooperate with the teeth situated on thesecond faces of those belts and are fitted between those teeth so as totranslate the belts whilst squeezing them against one another so thattheir facing studs engage one another.

According to the invention, the casing of the drive members alsocontains guide surfaces for the actuating belts, which guide surfacesare designed to enable the belts to bend in the region of the endlesscaterpillar-type bands in order to cause them to face one another sothat their respective studs can engage one another.

According to another characteristic of the invention, the studs of theactuating belts comprise two side faces as well as a front transverseactive face and a rear transverse active face each having a doublecurvature.

The front and rear transverse active faces of a stud of one of theactuating belts are caused to bear against the respective rear and fronttransverse active faces, respectively, of two associated adjacent studsof the other actuating belt when the two actuating belts are assembledintegrally.

It is essential, in order for the linear actuator according to theinvention to be able to perform its function, that the linear portiondefined by the two actuating belts when they are assembled integrallyshould not include “voids” and, therefore, that the geometry of theactuating belts should be such that the shape and dimensions of thespaces between the studs should be identical to those of the studs.

According to another characteristic of the invention, the front and reartransverse active faces of the studs comprise a double shoulder formingan abutment.

These shoulders prevent any transverse sliding of the adjacent studsrelative to one another when the two actuating belts are assembledintegrally.

According to another characteristic of the invention, the front and reartransverse active faces of the studs are separated by a substantiallyrectilinear, toothed longitudinal face.

The teeth of the longitudinal face of a stud of one of the belts arecaused to cooperate with corresponding teeth of the section of the firstface of the other belt situated between the two studs associated withthat stud, whilst being fitted between those teeth, when the twoactuating belts are assembled integrally.

As a result, in this position, the faring first faces of the twoactuating belts are intimately engaged over their entire length.

According to another characteristic of the invention, the two rotarypinions are extended coaxially by respective toothed extensions ofsmaller diameter cooperating with respective idle auxiliary gears of thesame diameter so as to drive the endless caterpillar-type bands.

According to the invention, the casing of the drive members may alsoadvantageously contain at least a pair of positioning rollers havingaxes substantially perpendicular to the axes of the rotary pinions andengaging on one side and on the other side of a linear portion of theactuator defined by the two integrally assembled actuating belts,against the side faces of the studs of those belts.

The characteristics of the linear actuator of the invention will bedescribed in greater detail with reference to the appended drawings, inwhich:

FIG. 1 is a diagram showing the linear actuator, in which the upperportion of the casing of the drive members has been removed,

FIG. 2 shows the two actuating belts,

FIG. 2 a is a section through FIG. 2, taken in a plane indicatedschematically by the axis II-II,

FIG. 3 shows a detail of the two actuating belts,

FIG. 4 is a diagram showing the drive members, in which the upperportion of the casing of these members has been removed,

FIG. 5 is a section through FIG. 4, taken in a plane indicatedschematically by the axis V V, the actuating belts being positioned inthe drive members,

FIG. 6 is a section through FIG. 4 taken in a plane indicatedschematically by the axis VI VI, the actuating belts being positioned inthe drive members.

According to FIG. 1, the linear actuator comprises two identicalactuating belts 1, 1′ as well as drive members 3 which drive theactuating belts 1, 1′ so as to translate them in one direction or in theother in accordance with the double arrows A, B and B′.

In the lower portion of FIG. 1, that is, upstream of the drive members3, the two actuating belts 1, 1′ are independent of one another whereas,in the upper portion of FIG. 1, that is, downstream of the drive members3, the two belts 1, 1′ are assembled integrally so as to define aportion which extends along a straight line and in which the linearactuator behaves as a unitary rigid bar.

According to FIGS. 2, 2 a and 3, the actuating belts 1, 1′ are providedon each of their races 10, 11 and 10′, 11′ with identical teeth 4, 4′which are caused, respectively, to fit between associated teeth in amanner which will be described in greater detail below.

A first face 10, 10′ of the actuating belts 1 is also equipped withuniformly-spaced studs 2, 2′ which are separated by toothed sections 5,5′.

Each stud 2, 2′ comprises two side faces 6, 6′ as well as a fronttransverse active face 7, 7′ and a rear transverse active face 8, 8′having a double curvature.

The front and rear transverse active faces 7, 7′, 8, 8′ of the studs 2,2′ are separated by a substantially rectilinear toothed longitudinalface 20, 20′.

As can be seen in particular in FIG. 3, the actuating belts 1, 1′ have ageometry which is designed in a manner such that the shape anddimensions of the spaces between the studs 2, 2′ are identical to thoseof the studs.

According to FIG. 3, the front and rear transverse active faces 7,7′,8,8′ of the studs 2,2′ also comprise a double shoulder 9 forming anabutment the function of which will also be explained below.

According to FIGS. 4, 5 and 6, the drive members 3 comprise a casing 12containing two rotary pinions 13, 13′ of the same diameter and of axisX-X′, which engage one another.

According to FIG. 5, one of these pinions 13 is a drive pinion and isconnected to a motor, not shown, by a drive axle 14 projecting from thecasing 12, whereas the second rotary pinion 13′ is a driven pinion.

According to FIGS. 4 and 5, the rotary pinions 13, 13′ are extendedcoaxially by respective extensions 15, 15′ equipped with teeth 16, 16′and having a smaller diameter.

According to FIG. 4, the toothed extensions 15, 15′ cooperate,respectively, with two idle auxiliary gears 17, 17′ of the same diameterand with parallel axes.

The rotary pinions 13, 13′ equipped with the toothed extensions 15, 15′and the auxiliary gears 17, 17′ also rotate two endless caterpillar-typebands 18, 18′ the inner faces of which art equipped, for this purpose,with teeth corresponding to the teeth of the extensions 15, 15′ and ofthe auxiliary gears 17, 17′.

These two endless bands 18, 18′ are caused to sandwich the two actuatingbolts 1, 1′ between them in order to guide the belts and translate themin one direction or in the other, according to the direction of rotationof the drive pinion 13.

For this purpose, the outer faces of the two caterpillar-type endlessbands 18, 18′ also have teeth 21, 21′ which can engage the teeth 4, 4′situated on the second faces 11, 11′ of the two actuating belts 1, 1′ inorder to translate the belts in accordance with the arrows A, B and B′.

According to FIGS. 1 and 4, the casing 12 of the drive members 3 alsocontains guide surfaces 19, 19′ for the two actuating belts 1, 1′; theguide surfaces 19, 19′ cooperate with the longitudinal faces 20, 20′ ofthe studs 2, 2′ of the belts in order to transfer the belts between theendless caterpillar-type bands 18, 18′ or to disengage them therefrom,by bending them.

According to FIG. 1, in the course of this transfer, when the drivepinion 13 turns clockwise, the studs 2, 2′ of the two actuating belts 1,1′ enter the casing 12 independently in the region of its side edges, onone side and on the other side of the casing, and are then guided so asto translate in its inner portion along the guide surfaces 19, 19′,respectively, in the region of which guide surfaces 19, 19′ the beltsare subjected to bending such that they are situated facing one anotherbefore entering between the two endless caterpillar-type bands 18, 18′.

In the region of these bands, the actuating belts 1, 1′ are squeezedagainst one another so that the studs 2, 2′ mesh with one another andthe two belts 1, 1′ are assembled integrally in a portion extendingalong a straight line.

For this purpose, the front and rear transverse active faces 7, 7′, 8,8′ of the studs 2, 2′ of one of the actuating belts 1, 1′ bear,respectively, against the rear and front transverse active faces 8′, 8,7′, 7 of the two associated adjacent studs 2′, 2 of the other actuatingbelt 1′, 1′ and the teeth 4, 4′ of the longitudinal faces 20, 20′ of thestuds 2, 2′ of one of the actuating belts 1, 1′ engage, respectively, inthe corresponding teeth of the respective section 5′ 5 of the otheractuating belt 1′, 1 separating the two associated adjacent studs 2′, 2,so that the two actuating belts are fitted together perfectly to definea unitary rigid bar.

In this position, the double abutment shoulders 9 provided on thetransverse active faces 7, 7′; 8, 8′ prevent any transverse sliding ofthe adjacent studs 2, 2′ relative to one another.

Naturally, when the drive pinion 13 turns anticlockwise, thedisplacement of the studs 2, 2′ of the two actuating belts 1, 1′ takesplace in the opposite direction, that is, the studs enter the casing 12fitted together and are separated at the level of the twocaterpillar-type endless bands 18, 18′.

Moreover, and according to FIGS. 4 and 6, the casing 12 also enclosestwo pairs of positioning rollers 22.

Each of these pairs is constituted by a combination of two positioningrollers 22 ₁, 22 ₂ of axis Y-Y′ perpendicular to the axes X-X′ of therotary pinions 13, 13′.

These positioning rollers 22 ₁, 22 ₂ engage against the side faces 6, 6′of the studs 2, 2′ in order to ensure the correct positioning of theactuating belts 1, 1′ when they are fitted together.

1. A linear actuator for transmitting tractive and thrust forces, saidactuator comprising: first and second flexible actuating belts, eachsaid actuating belts having an inner face and an outer face, each saidinner faces including a plurality of spaced apart studs disposedthereon, said studs spaced apart by spaces of equal length, a firsttooth disposed on said inner faces in each said spaces of both saidactuating belts, each said space associated with each said belt shapedto form fittingly receive therein a said stud disposed on the other saidactuating belt to thereby completely fill said space, each said studsincluding first and second side faces, a front active face, a rearactive face, and a substantially rectilinear face disposed between saidfront active face and said rear active face, each said rectilinear facehaving a second tooth disposed thereon, said outer faces of saidactuating belts each having a plurality of third teeth disposed thereon;a control member operatively associated with said first and second beltsto cause the plurality of studs disposed on said first and second beltsto mesh with one another, said control member comprising a pair oftoothed members, each said toothed member having a plurality of fourthteeth operatively arranged to mesh with said plurality of third teeth,so that when said first and second teeth are caused to mesh by saidcontrol member, said studs of said respective first and second belts areeach form fittingly received in said spaces of said respective secondand first belts, each of said plurality of said first teeth of saidrespective first and second belts are engaged with said second toothassociated with said respective second and first belts, and saidplurality of third teeth of said respective first and second belts areeach engaged with said plurality of fourth teeth of one of said toothedmembers, wherein said meshed belts are independent upstream of saidcontrol member and form a unitary rigid member downstream of saidcontrol element without voids between said studs.
 2. The linear actuatorof claim 1 wherein said first and second actuating belts are comprisedof a reinforced plastic material.
 3. The linear actuator of claim 1wherein said first teeth, said second teeth, and said third teeth areidentical in shape.
 4. The linear actuator of claim 1 wherein each saidfront and said rear active faces are S shaped.
 5. The linear actuator ofclaim 1 wherein each said front and said rear active faces include adouble shoulder to thereby prevent said meshing studs from transverselysliding relative to one another downstream of said control element. 6.The linear actuator of claim 1 wherein said toothed members comprise twoendless belts, each said endless belts having first and second sides,said fourth teeth located on a first side of each said respectiveendless belts, said control member further comprising a rotatabledriving pinion and a rotatable driven pinion, said driving piniondrivingly engaging said driven pinion and said two endless belts.
 7. Thelinear actuator of claim 6 wherein each said driving and driven pinionsinclude a toothed extension, said control member further including twoauxiliary idler gears, said respective toothed extensions and auxiliaryidler gears directly engaging said respective endless belts.
 8. Thelinear actuator of claim 6 wherein said control member further includesa plurality of positioning rollers for engaging said side faces.